The present invention relates to a tip seal in a scroll fluid machine and particularly to a tip seal that fits in a tip-seal groove on the end faces of an orbiting wrap and a stationary wrap.
A scroll fluid machine such as a scroll compressor and a scroll vacuum pump comprises a drive shaft having an eccentric axial portion at one end; an orbiting scroll pivotally connected on the eccentric axial portion via a bearing and having an orbiting wrap on an orbiting end plate; a stationary scroll having a stationary wrap on stationary end plate; and a plurality of self-rotation preventing devices for preventing the orbiting scroll from rotating on its own axis. With engagement of the stationary wrap with the orbiting wrap, a sealed chamber is formed between them.
With the self-rotation preventing devices and eccentric axial portion, the orbiting scroll is eccentrically revolved, so that the volume in the sealed chamber gradually decreases toward the center or gradually increases away from the center thereby guiding a gas sucked from the outer circumference with compression or a gas sucked from the center with decompression.
The orbiting and stationary wraps are made based on an involute curve gradually increasing in diameter in a direction of rotation, a curve which comprises connected short arcs in a circumferential direction around the center or combination thereof. A gap in a radial direction between the orbiting and stationary wraps is exactly determined not to contact the wraps to each other or not to be too large.
A tip seal groove is formed on the end faces of the orbiting and stationary scrolls and a tip seal fits in a tip-seal groove to allow the facing ends to slide hermetically.
In order to make sealing capability better between the end plates, a backup material is put on the bottom of the tip-seal groove. A sealing material made of resin is bonded on the backup material with adhesive.
JP6-207588A discloses heat-resistant elastic material in FIG. 3 and JP3248618B discloses porous material softer than sealing material or a band-shaped elastic material made of heat-resistant rubber.
When a scroll fluid machine is used under high temperature or high radioactivity, adhesive between the backup material and sealing material changes in quality or deteriorates to lose adhesive force and to become powder which invades each sliding part thereby decreasing sealing capability and leaking to the outside which results in environmental contamination.
In the backup material bonded to the sealing material, if one of them is not suitable in use, both the materials have to be replaced or abandoned which is not economical.
It will be useful if the backup material and sealing material fit in the tip-seal groove at the ends of the ordinary or stationary wraps to achieve desired function without bonding the backup material to the sealing material.
However, if both are not integrally bonded, sealing capability is not completely kept in bonding surfaces, so that required gas-tightness cannot be achieved.
Furthermore, if the backup material is not integrally connected to the sealing material, it will not be easy to keep their sideward relationship exact to cause troublesome assembling and/or disassembling of them into and/or from the tip-seal groove before and after engagement into the tip-seal groove since they have a small cross-section and are long.